Best way I could put it is, have you ever driven an old American car 80's Cadillac Coupe De Ville (my dad had one) felt very disconnected, might as well drive the car with a chicken leg as sometimes you dont feel turning the wheel directly relates to turning the car. When I played a game without FFB I got that same feeling, I mean the wheel centers and all but immersion is gone, then you get complacent with your surroundings. When you run over dirt or skid your wheel will go slack and you instinctivly divert your concentration to getting back traction. Without FFB you may forget it and think you are fine when you are not.
With my dads Caddy, I never knew I was in control of that car, but that was how I thought all cars were back then, until he got a Datsun 280z.